JP2015032800A - Lithographic apparatus and article manufacturing method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a lithographic apparatus that is advantageous in terms of positioning accuracy of a substrate holding unit.SOLUTION: A lithographic apparatus includes: a substrate holding unit that is movable while holding a substrate; a measuring station that includes a first measuring instrument, which includes a first reference member and measures a height of the substrate holding unit, and a second measuring instrument, which measures a height of a surface of the substrate held by the substrate holding unit; a pattern forming station that includes a third measuring instrument, which includes a second reference member and measures the height of the substrate holding unit, and in which pattern formation is performed on the substrate held by the substrate holding unit on the basis of an output of the second measuring instrument, and a control unit. Here, the pattern forming station includes a fourth measuring instrument that measures the height of the surface of the substrate held by the substrate holding unit. The control unit obtains a correction value related to an output obtained from at least one of the first measuring instrument and the third measuring instrument on the basis of outputs of the second measuring instrument and the fourth measuring instrument concerning the substrate held by the substrate holding unit (S106).

Description

  The present invention relates to a lithographic apparatus and an article manufacturing method.

  An exposure apparatus exposes a substrate (such as a wafer or a glass plate having a resist layer formed on the surface) through a pattern of an original (such as a reticle) in a lithography process included in a manufacturing process of a semiconductor device or a liquid crystal display device. Device. In this exposure apparatus, as the NA (numerical aperture) of the projection optical system for forming the pattern image on the substrate increases, very high accuracy is required for focus and leveling adjustment by the substrate stage. For example, the depth of focus that can be secured during exposure is approximately 200 [nm] with a scanning exposure apparatus with NA = 0.93. Now consider the accuracy of control that can be assigned to focus and leveling adjustments. At this time, the accuracy is generally 10% (about approximately 10%) by removing error factors such as curvature of field, defocus amount of reticle factor, and calibration (measurement) error of image plane from the depth of focus. 20 [nm]). Therefore, conventionally, the focus (Z-axis) and leveling (ωx, ωy) measurement can measure the distance between the upper surface of the stage (top plate surface) and the surface plate on which the projection optical system is fixed, and linearity. Measuring instruments including laser interferometers with good resolution are used.

  On the other hand, Patent Document 1 discloses an exposure apparatus including a plurality of substrate stages in one apparatus in order to improve throughput. In this exposure apparatus, for example, two areas on the surface plate, that is, a first area (exposure station) for performing exposure, and a second area (measurement station) for performing measurement (alignment measurement) on the substrate before exposure are provided. There is. According to this configuration, the first substrate held on the other substrate stage in the exposure station while performing measurement on the second substrate held on the one substrate stage in the measurement station. Can be exposed to.

Japanese Patent Publication No. 10-163099

  The exposure apparatus of Patent Document 1 includes a ZX bar mirror as one of plane mirrors (reference members) used for measurement by a laser interferometer. The ZX bar mirror is installed on the surface plate (the surface plate supporting the projection optical system or the measuring device) of each of the exposure station and the measurement station so as to face the substrate stage. Therefore, since the exposure station and the measurement station refer to different ZX bar mirrors, if there is a relative shape error between the two ZX bar mirrors, a focus error may occur in the exposure station. Further, since leveling (particularly ωy) is based on measurement values obtained by different ZX bar mirrors, an error may occur in the same manner.

  Such a relative shape error of the ZX bar mirror is roughly classified into an error that can be corrected before the operation of the apparatus due to processing, assembly, installation, and the like, and a time-dependent error that appears after the operation of the apparatus. Of these, the former can be corrected by measuring the shape error of the ZX bar mirror between both stations and storing the corresponding correction value in the memory. On the other hand, for the latter, first, the component of the shape error less than the second order with respect to X in the Z-X plane, such as the entire ZX bar mirror being shifted in the Z-axis direction or the entire ZX bar mirror being tilted, It can be corrected by aligning the origin. Here, the component of the shape error less than the second order refers to the 0th order and the first order components with respect to X in Z = f (X). However, a secondary or higher-order shape error component such as a bow cannot be corrected by origin matching. Therefore, the temporal change of the second-order or higher component of the relative shape error between the two ZX bar mirrors leads to a decrease in positioning accuracy, and the projected image is blurred (relative inclination between the substrate surface and the image surface). This may cause defocusing including blurring due to blurring.

  An object of the present invention is to provide a lithographic apparatus that is advantageous in terms of the positioning accuracy of a substrate holder, for example.

  In order to solve the above-described problem, the present invention provides a lithography apparatus that forms a pattern on a substrate, includes a movable substrate holding portion that holds the substrate, and a first reference member, and the height of the substrate holding portion is increased. A measurement station that includes a first measuring instrument that measures and a second measuring instrument that measures the height of the surface of the substrate held by the substrate holder, and a second reference member that measures the height of the substrate holder. A pattern forming station including a third measuring instrument that performs pattern formation on the substrate held by the substrate holder based on the output of the second measuring instrument, and a control unit. Includes a fourth measuring instrument that measures the height of the surface of the substrate held by the substrate holding unit, and the control unit outputs the output of the second measuring instrument related to the substrate held by the substrate holding unit and the fourth measuring instrument. And the first measuring instrument and the third based on the output Obtaining a correction value of the output obtained from at least one of the measuring instruments, characterized in that.

  According to the present invention, for example, it is possible to provide a lithographic apparatus that is advantageous in terms of positioning accuracy of a substrate holding portion.

It is a figure which shows the structure of the exposure apparatus which concerns on one Embodiment of this invention. It is a figure which shows the structure of a 1st focus position measurement part. It is a figure which shows the structure of a 2nd focus position measurement part. It is a figure which shows arrangement | positioning of the position measurement system of a wafer stage. It is a figure which shows the measurement point of the focus set on the wafer. It is a flowchart which shows the correction process of a bar mirror shape error. It is a graph which shows the measurement result by each focus position measurement part, and its difference. It is a flowchart which shows the data processing process of the measured value by each position measurement system. It is a flowchart which shows an error processing process.

  Hereinafter, embodiments for carrying out the present invention will be described with reference to the drawings.

  First, the configuration of a lithography apparatus according to an embodiment of the present invention will be described. The lithography apparatus is an apparatus that forms a pattern on a substrate such as a wafer. Hereinafter, the lithography apparatus according to the present embodiment will be described as an exposure apparatus as an example. FIG. 1 is a schematic diagram showing a configuration of an exposure apparatus 1 according to the present embodiment. In FIG. 1, the Z-axis is taken in parallel to the optical axis (vertical direction in the present embodiment) of the projection optical system 4 to be described later, and the Y-axis is taken in the scanning direction of the wafer W during exposure within a plane perpendicular to the Z-axis. The X axis is taken in the non-scanning direction orthogonal to the Y axis. As an example, the exposure apparatus 1 is a projection type that is used in a semiconductor device manufacturing process and exposes a pattern formed on a reticle R on a wafer W (on a substrate) by a step-and-scan method. Here, the step-and-scan method refers to a method in which an exposure area is formed into a long and narrow slit shape, and the exposure area is scanned while the reticle R and the wafer W are synchronized. Further, since the exposure apparatus 1 corresponds to the projection optical system 4 with NA ≧ 1.0, the exposure apparatus 1 is an immersion type in which the space between the wafer W and the final lens of the projection optical system 4 is locally filled with a liquid such as pure water. To do. A supply nozzle that supplies liquid onto the wafer W, a discharge nozzle that discharges liquid after exposure, and the like are not shown. Further, the exposure apparatus 1 includes a wafer stage 6 having a plurality of stages for holding the wafer W in the apparatus. In particular, in this embodiment, the exposure apparatus 1 is a so-called twin stage type including two wafer stages 6 as an example. First, the exposure apparatus 1 includes an exposure station 100, a measurement station 200, a control unit 300, and a wafer transfer system 400.

  The exposure station (pattern forming station) 100 includes an illumination system 2, a reticle stage 3, a projection optical system 4, and a first focal position measurement unit 5. The illumination system 2 shapes the light emitted from the light source 2 a into a predetermined beam shape, and irradiates the reticle R held on the reticle stage 3. The light source 2a outputs light of a plurality of wavelength bands, for example, light from a mercury lamp, ArF excimer laser, KrF excimer laser, or the like as exposure light. The reticle R is, for example, a glass original plate on which a fine circuit pattern is formed. The projection optical system (projection system) 4 reduces the image of the circuit pattern on the reticle R at a predetermined reduction magnification, and forms an image on a shot set on the wafer W.

  FIG. 2 is a schematic diagram illustrating the configuration and measurement principle of the first focal position measurement unit 5. The first focal position measurement unit (fourth measuring instrument) 5 may be, for example, a TTL (Through The Lens) type image detection system as shown in FIG. The light beam emitted from the light source 10 enters the illumination system 2 for exposure and is divided into exposure light and non-exposure light. Of the divided light, non-exposure light is guided to the illumination system of the first focal position measurement unit 5 through a routing system 11 including an optical fiber, a lens, a mirror, and the like. The light emitted from the illumination system is limited in light flux by an oblique entrance aperture stop provided at a position substantially conjugate with the aperture stop surface of the projection optical system 4, that is, the so-called pupil plane. The oblique incident aperture stop has a slit-like opening at a position shifted in the Y-axis direction from the optical axis, and the measurement light that has passed through the objective lens is obliquely incident on the surface position measurement mark at this incident angle. The surface position measurement mark is formed on the reticle reference plate 12 and includes a portion that transmits the measurement light and a portion that reflects (shields) the measurement light. The light (wafer reflected light) transmitted by the surface position measurement mark passes through the projection optical system 4 and enters the wafer W on the wafer stage 6, is reflected on the wafer W, and passes through the projection optical system 4 again. After that, the image sensor 13 receives the light. On the other hand, the light reflected by the surface position measurement mark (reticle reflected light) passes through the objective lens 14 and is then received by the image sensor 13. As a result, a line pattern of the reticle reflected light and the wafer reflected light is imaged on the image sensor 13. In this line pattern, the reticle reflected light and the wafer reflected light do not coincide with each other, and there is a deviation of ΔY. This deviation is a value depending on the shift amount of the aperture on the oblique incident aperture stop and the drive amount of the wafer stage 6 in the Z-axis direction. In this embodiment, since the opening shift amount is constant, the deviation amount ΔY is considered to be an amount that depends only on the Z-axis direction. The first focal position measurement unit 5 emits reticle reflected light and wafer reflected light at regular intervals while illuminating the surface position measurement mark while the wafer stage 6 is scanned or step-driven in the Y-axis direction. Take an image. The surface of the wafer W is not a perfect plane but has irregularities. Accordingly, the surface position of the wafer W at the measurement point of the first focal position measurement unit 5 slightly changes by ΔZ in the Z-axis direction according to the unevenness. This minute change ΔZ is detected as a minute shift ΔYd of the wafer reflected light on the detection surface of the image sensor 13. At this time, since the reticle stage 3 is not driven (moved), no shift of reticle reflected light on the detection surface of the image sensor 13 occurs. Therefore, the first focal position measurement unit 5 can identify the minute shift ΔYd with reference to the reticle reflected light, and can identify the minute change ΔZ from the minute shift ΔYd. The first focus position measurement unit 5 then moves the focus position (Z axis) and the leveling direction (particularly the ωy direction) of the wafer stage 6 in accordance with the displacement of the surface position of the wafer W based on the minute change ΔZ. Can be measured.

  The measurement station 200 includes an off-axis scope (OAS) 20 and a second focal position measurement unit 21. The OAS 20 detects the alignment mark and measures the amount of positional deviation in the X-axis and Y-axis directions on the measurement axis. Specifically, the OAS 20 determines the relative position and posture relationship between an alignment mark on the wafer W placed on the wafer stage 6 and a reference mark 55 on the wafer stage 6 (fine movement stage 41) described later. Measurement is performed while the stage 6 is moved relative to the design coordinate value.

  FIG. 3 is a schematic diagram illustrating the configuration and measurement principle of the second focal position measurement unit 21. The second focal position measurement unit (second measuring instrument) 21 can measure the surface shape of the wafer W (focus map information on the entire surface) by measuring the focal positions of a plurality of points on the surface of the wafer W. The second focal position measurement unit 21 includes, for example, a light projecting system 22 that projects a plurality of light beams onto the wafer W at a high incident angle (angle θ), and a light receiving system 23 that receives light reflected from the wafer W. And a signal processing unit 24. The light projecting system 22 includes a light source 25, a pattern plate 26, an imaging lens 27, and a mirror 28. In the example shown in FIG. 3, lenses for illuminating the pattern plate 26 with a uniform illuminance distribution, lenses for correcting chromatic aberration, and the like are not shown. The light source 25 is an LED, a halogen lamp, or the like, and illuminates the pattern plate 26 with light having a wavelength λ1. The pattern plate 26 is formed with three rectangular slit patterns M1, M2, and M3 (longitudinal direction is the X-axis direction) in the light shielding portion, and the light that has passed through the slit patterns M1, M2, and M3 is an imaging lens. The projection image is formed on the wafer W through the mirror 27 and the mirror 28. On the other hand, the light receiving system 23 includes a mirror 29, a lens 30, and a two-dimensional image sensor 31. The light (pattern image) reflected by the wafer W is received (re-imaged) by the two-dimensional image sensor 31 which is, for example, a CMOS sensor via the mirror 29 and the lens 30. Here, when the wafer W moves in the vertical direction (Z-axis direction) by driving the wafer stage 6, the pattern image of the pattern plate 26 moves in the Y-axis direction on the imaging surface of the two-dimensional image sensor 31. Therefore, the second focal position measurement unit 21 can detect the surface position of the wafer W for each measurement point by deriving the position of the pattern image by the signal processing unit 24. The displacement amount Y of each spot on the imaging surface of the two-dimensional imaging device 31 with respect to the displacement Z in the Z-axis direction of the surface position of the wafer W is M for the optical magnification of the light receiving system 23 and θ for the incident angle on the wafer W. Then, Y = (2Msin θ) × Z. That is, the displacement Z is expressed as Z = Y / (2Msin θ). Then, the second focal position measurement unit 21 can measure the focal position by moving the wafer stage 6 in the focus and leveling direction in accordance with the displacement of the surface position of the wafer W based on the displacement Z.

  In addition, although the 1st focus position measurement part 5 and the 2nd focus position measurement part 21 are not represented by a figure, in the example of arrangement | positioning shown in FIG. This is because if each of the stations 100 and 200 has only one focus position measurement unit 5 and 21, only the measurement result in the focus direction can be obtained. Therefore, the leveling direction (a plane parallel to the Z-axis direction) can be obtained. This is a measure for obtaining a measurement result of (tilt). Further, in this case, in order to set the measurement image heights of the first focal position measurement unit 5 and the second focal position measurement unit 21 to the same coordinates, the attachment intervals (arrangement intervals) in the X-axis direction may be equalized. desirable. In the above configuration, the focus measurement by the first focus position measurement unit 5 and the focus measurement by the second focus position measurement unit 21 are performed while scanning the wafer stage 6 to reduce the time taken to measure the focus map information. Desirable for shortening.

  The wafer stage (substrate holding unit) 6 is movable, for example, by sucking and holding the wafer W via the chuck 7. In particular, in the present embodiment, a twin stage type exposure apparatus 1 is illustrated. In this case, two wafer stages 6 (first wafer stage (first substrate holding part) 6A, second wafer stage (second substrate holding) Part) 6B). Each of these wafer stages 6 can be moved between the exposure position in the exposure station 100 and the alignment measurement position in the measurement station 200 (the positions are switched alternately). According to the wafer stage 6, for example, exposure of the first wafer (first substrate) W1 on the first wafer stage 6A at the exposure station 100 and second wafer (on the second wafer stage 6B at the measurement station 200). Measurement for the second substrate W2 can be performed in parallel.

  FIG. 4 shows a configuration of the wafer stage 6 and a position measurement system for measuring the position of the wafer stage 6 installed in each station 100, 200 (the distance is specified and the position is specified. Is a schematic perspective view showing. The configuration of the wafer stage itself is the same for both the first wafer stage 6A and the second wafer stage 6B. The wafer stage 6 is provided with a coarse movement stage 40 that can move on the XY plane, and a chuck 7 (not shown in FIG. 4) that is mounted on the coarse movement stage 40 and directly holds the wafer W. And a fine movement stage 41 operable with six axes for directional tilt correction.

  First, the position of fine movement stage 41 in each of the XY axes is determined by an X-axis interferometer (X interferometer) 42 and a Y-axis interferometer (Y interferometer) 43 which are laser interferometers as length measuring mechanisms. It is measured by. The X interferometer 42 measures the position in the X-axis direction by irradiating and reflecting a laser beam onto an X-bar mirror (planar mirror) 44 extending on the Y-axis direction side surface of the fine movement stage 41. On the other hand, the Y interferometer 43 measures the position in the Y-axis direction by irradiating and reflecting a laser beam to a Y-bar mirror (not shown) extending on the side surface in the X-axis direction of the fine movement stage 41. In accordance with the X interferometer 42 and the Y interferometer 43, an X-axis yaw direction interferometer (laser interferometer) that is spaced apart in the horizontal direction on either or both sides of the X-axis and the Y-axis ( X-yaw interferometer) 44 and Y-axis yaw direction interferometer (Y-yaw interferometer) 45 are installed. A displacement amount ωz in the rotational direction of the fine movement stage 41 in the XY plane is measured by the X yaw interferometer 44 and the Y yaw interferometer 45. Further, the rotation ωx around the X-axis of fine movement stage 41 is a tilt interferometer that is a laser interferometer that is installed side by side with a gap Δz in the vertical direction with no positional deviation with respect to Y interferometer 43. 47.

Further, the position of fine movement stage 41 in the Z-axis direction is a Z-axis direction first interferometer (first Z interferometer) 48 and a Z-axis direction second interferometer (laser interferometers as a length measuring mechanism). 2nd Z interferometer) 51. The set of these two interferometers is a first measuring instrument on the measuring station 200 side and a third measuring instrument on the exposure station 100 side with respect to the previously described second measuring instrument and fourth measuring instrument. You can also see it. Among these, the first Z interferometer 48 is an interferometer installed on the X interferometer 42 side. The laser emitted from the first Z interferometer 48 is reflected by the ZY bar mirror 49 extending to the Y-axis direction side surface of the fine movement stage 41 while changing the traveling direction in the + Z direction (upward in the Z-axis direction). The laser whose traveling direction has changed is reflected in the −Z direction (downward in the Z-axis direction) by a ZX bar mirror (a plane mirror as a reference member) 50 installed on the lens barrel surface plate 65 (see FIG. 1). Return to the first Z interferometer 48. Here, let the component in the focus direction obtained by the first Z interferometer 48 be ZR. Similarly, a second Z interferometer 51, a ZY bar mirror 52, and a ZX bar mirror (a plane mirror as a reference member) 53 are installed on the opposite side of the first Z interferometer 48 with respect to the fine movement stage 41. Here, let the component in the focus direction obtained by the second Z interferometer 51 be ZL. The ZX bar mirrors 50 and 53 on the measurement station 200 side can be viewed as first reference members, whereas the ZX bar mirrors 50 and 53 on the exposure station 100 side can be viewed as second reference members. Thus, the position of the Z-axis direction on the whole surface of the XY plane with two Z interferometers 48 and 51 is measured, by taking an average value, correct the position Z _pos in the Z axis direction of the fine moving stage 41 Can be measured. In this case, the position Z _pos can be obtained from the relationship of Z _pos = (ZL + ZR) / 2. The component ωy _{pos in the} ωy direction can also be obtained from the relationship of ωy _pos = (ZL−ZR) / L by taking the difference between ZL and ZR. However, L is the distance in the X-axis direction from the point where the laser hits the ZY bar mirror 49 to the point where the laser hits the ZY bar mirror 52.

  The fine movement stage 41 includes two sensor units 56 each including two LIPS sensors 54 and a reference mark 55 arranged on the surface thereof (on the stage top plate) with an interval in the X-axis direction. Have In the exposure apparatus 1, after the wafer stage 6 moves between the stations, the exposure irradiation light is allowed to pass between a LIPS mark (not shown) drawn in advance as a reticle design on the reticle R and the LIPS sensor 54. Alignment is performed. This alignment corrects the offset deviation in the focus and leveling directions. Hereinafter, this correction principle will be described in detail. For example, the focus map information of the wafer W (first wafer W1) on the first wafer stage 6A measured by the measurement station 200 is stored as a difference value of Z and ωy components relative to the reference plane of the LIPS sensor 54. Is done. The first wafer stage 6A that has completed the acquisition of the focus map information and the XY alignment measurement of the first wafer W1 is replaced with the second wafer stage 6B on the exposure station 100 side, and the exposure station 100 (just below the projection optical system 4). Exposure position). Next, an aerial image measurement of the LIPS mark is performed between the LIPS mark on the reticle R and the two LIPS sensors 54 on the first wafer stage 6A, and the X, Y, Z, ωz, The origin of the ωy axis component is aligned. Next, a desired shot position is determined based on the exposure sequence and shot arrangement defined in advance as a recipe, the alignment measurement result obtained by the measurement station 200, and focus map information. Then, exposure is performed after correcting offset deviation in the focus and leveling directions based on them.

  The control unit 300 can perform operation control of various measurement units and drive units included in the exposure apparatus 1, processing of focus map information and alignment measurement results, and calculation processing of a stage target trajectory during exposure. The control unit 300 is configured by a computer, for example, and is connected to each component of the exposure apparatus 1 via a line, and can control each component according to a program or the like. Further, the control unit 300 may be configured integrally with another part of the exposure apparatus 1 (in a common casing), or separate from the other parts of the exposure apparatus 1 (in a separate casing). It may be configured.

  Of the above components, the reticle stage base surface plate 62 that supports the illumination system 2 and the reticle stage 3 is supported by a support body 61 that extends in the Z-axis direction from a base surface plate 60 installed on the floor surface. Supported. The reticle stage base surface plate 62 receives the load of the reticle R, and the reaction force generated by the reticle drive is canceled by the drive of the counter mass (not shown). The projection optical system 4 is supported by a lens barrel surface plate 65 supported from a base surface plate 60 via a support column 64 while being vibrationally insulated by a damper (vibration isolation member) 63. The various laser interferometers as the position measurement system of the wafer stage 6 described with reference to FIG. 4 and the ZX bar mirrors 50 and 53 are also supported by the lens barrel surface plate 65. The wafer stage 6 is supported by a wafer stage surface plate (not shown) laid on the base surface plate 60, and moves between the stations on the wafer stage surface plate.

  The wafer transfer system 400 can place a FOUP 70 that accommodates a wafer W to be processed, and a first hand 71 for mounting the wafer W on the wafer stage 6 in the measurement station 200 from the FOUP 70 and for recovery. The second hand 72 is provided. In addition, since the exposure apparatus 1 is a liquid immersion type, the wafer transfer system 400 includes a lid wafer 73 that allows a liquid film to be maintained at the exposure station 100 even when the wafer W is not supplied onto the wafer stage 6, and a lid. A maintenance carrier 74 for accommodating the wafer 73 is mounted.

  Here, the alignment of the wafer stage 6 in the focus and leveling direction described with reference to FIG. 4 is based on the premise that the shapes of the ZX bar mirrors 50 and 53 included in the length measuring mechanism are not deformed. However, each ZX bar mirror 50, 53 correlates with time or with changes in environmental temperature, and deforms although it is a minute amount. Such deformation may cause a difference in measurement values obtained by various laser interferometers on the exposure station 100 side and the measurement station 200 side. This results in differences in alignment in the focus and leveling directions, and this difference can cause blurring and defocusing of the exposure result. Therefore, in the present embodiment, the movement error of the wafer stage 6 caused by the shape change (relative shape error) of each ZX bar mirror 50, 53 at each station 100, 200 is corrected as follows, and the exposure apparatus 1 is corrected. As a performance guarantee and self-correction function.

  Next, an operation (exposure method) for correcting the movement error of the wafer stage 6 caused by the shape change of each ZX bar mirror 50, 53 in the exposure apparatus 1 will be described. First, before specific description of the correction process, an example of the arrangement of the measurement points MP on the wafer W that the first focal position measurement unit 5 and the second focal position measurement unit 21 set as the measurement target (same target location) will be described. To do.

  FIG. 5 is a plan view illustrating a measurement point MP that is a position at which the focus set on the wafer W is measured. A relative error in the shape of each ZX bar mirror 50, 53 can occur when the wafer stage 6 moves in the X-axis direction. This is because the positions of the laser beams from the first Z interferometer 48 and the second Z interferometer 51 reflected by the ZX bar mirrors 50 and 53 move in the X-axis direction as the wafer stage 6 moves. When the wafer stage 6 moves in the Y-axis direction, the laser beams from the first Z interferometer 48 and the second Z interferometer 51 are reflected at one point on each ZX bar mirror 50, 53. , 53 does not affect the measurement value. Therefore, in the following five examples as FIG. 5, the measurement points MP are all arranged in the X-axis direction.

  FIG. 5A is a diagram in which measurement points MP are arranged on a straight line passing through the center point on the surface of the wafer W. FIG. When it is desired to measure the shape error of each ZX bar mirror 50, 53, the wafer stage 6 moves in the X-axis direction, so the arrangement of the measurement points MP is as simple as this. According to this arrangement, the longest possible distance in the X-axis direction can be measured. Note that if only one row of measurement point groups is measured once, there is a possibility that measurement errors from the first focal position measurement unit 5 and the second focal position measurement unit 21 may be affected. Therefore, even if the same wafer W is measured a plurality of times or the same measurement point MP is measured a plurality of times, it is possible to statistically improve the accuracy, reduce the standard deviation of the measurement result, and reduce the measurement error. Good.

  FIG. 5B is a diagram in which measurement points MP are arranged on the entire surface of the wafer W at equal intervals. According to this arrangement, since the entire surface of the wafer W can be measured, the measurement error can be reduced by the averaging effect as compared with the arrangement example of FIG. Note that the measurement interval at this time can be appropriately changed according to the conditions required at that time. For example, by narrowing the measurement interval, more detailed information can be obtained. On the other hand, if the measurement interval is widened, only rough information can be obtained, but the measurement time can be shortened. .

  FIG. 5C is a diagram in which many measurement points MP are arranged only at specific positions on the surface of the wafer W. Such an arrangement is applied when, for example, it is known in advance that specific portions of the ZX bar mirrors 50 and 53 are deformed due to changes over time or changes due to thermal expansion. According to this arrangement, the wafer stage 6 is frequently aligned with the specific position by reducing the measurement interval at the specific position. At the time of this alignment, the shape of the ZX bar mirrors 50 and 53 is referred to one by one, so that the state of deformation of the specific part is observed in detail. For measurement points other than the specific position, assuming that the deformation of each ZX bar mirror 50, 53 is small, the measurement interval may be wider than the arrangement example of FIG. Alternatively, as long as it can be assumed that the shapes of the ZX bar mirrors 50 and 53 in other parts are not substantially changed, there are no measurement points other than the specific position. That is, in the arrangement example shown in FIG. 5C, the measurement intervals of the ZX bar mirrors 50 and 53 are made dense by appropriately changing the measurement interval of the focus measurement on the wafer W, thereby further reducing the measurement time. It can be said that.

  Here, in the case of applying each arrangement example shown in FIGS. 5A to 5C, since an arbitrary measurement point MP on the surface of the wafer W is measured at the time of measurement, the wafer W to be measured is measured. For example, it is desirable to use a bare silicon wafer having as little as possible unevenness such as a base pattern. Further, when measuring the measurement point MP, it is desirable that the pattern is not developed on the wafer W. In the periodic maintenance, the lid wafer 73 accommodated in the maintenance carrier 74 in the wafer transfer system 400 may be used as a bare silicon wafer.

  FIG. 5D and FIG. 5E both show shots set in advance on the wafer W when the wafer W to be measured is not a bare silicon wafer but a process wafer to be actually processed. It is the figure which has arrange | positioned measurement point MP according to the arrangement | sequence. In particular, the arrangement example shown in FIG. 5 (d) arranges nine measurement points MP in one shot, while the arrangement example shown in FIG. 5 (e) has one point in one shot. Measurement points MP are arranged. As described above, the alignment of the wafer stage 6 in the focus and leveling direction is performed for each shot based on measurement at relatively the same position in the shot array. If the measurement is not performed in this way, the measurement value changes due to the influence of the unevenness of the circuit pattern already developed on the surface of the wafer W. According to these arrangements, the influence of the unevenness of the circuit pattern can be suppressed.

  In each arrangement example of FIG. 5, the measurement point MP is set on the surface of the wafer W, but the measurement point may be outside the wafer W. For example, FIG. 4 illustrates the mirror member 57 installed on the surface of the fine movement stage 41 (on the stage top). The mirror member 57 replaces the wafer W to be measured in this case, and by using this, each ZX bar mirror 50 in a portion that could not be measured only by the measurement point MP set on the surface of the wafer W, There is an advantage that the shape change of 53 can be known.

  FIG. 6 is a flowchart showing a correction process for correcting a change (shape error) in the shape (flatness) of each ZX bar mirror 50, 53 included in the length measuring mechanism in the present embodiment. Here, this correction process is required individually for each of the wafer stages 6A and 6B, but the series of flows shown in FIG. 6 is performed for one wafer stage 6. This correction process is performed every time a predetermined number of wafers (specified number) are processed, or every time a predetermined time (specified time) elapses. However, the timing at which the correction process is performed is not limited to these, and may be performed automatically, for example, immediately after power-on or when the exposure apparatus 1 is in an idle state. Further, when correction is performed every specified number of sheets or every specified time, the correction process is performed on the other wafer stage 6 while the wafer W to be processed is exposed on one wafer stage 6. Good.

  First, the control unit 300 causes the wafer station 6 to perform origin position alignment (stage alignment) at the measurement station 200 (step S101). Specifically, the control unit 300 causes the OAS 20 to detect two reference marks 55 on the wafer stage 6 (for example, the first wafer stage 6A, the same applies hereinafter), and based on the detection result, X, Y, Z , Ωx, ωy are adjusted so that the position of the wafer stage 6 becomes the value of the origin.

  Next, the control unit 300 measures the surface shape of the wafer W at the measurement station 200 and obtains focus map information (second position as focus position measurement information) (step S102). Specifically, the control unit 300 measures the second focus position measurement unit 21 while moving the first wafer stage 6A in the X-axis and Y-axis directions while maintaining the target value of the focus leveling axis at a constant value. The focus measurement (and leveling measurement) of the point MP is performed. Here, the focal position measurement information obtained by the second focal position measurement unit 21 is converted into the relative displacement amounts of the Z and ωy axes from the reference mark 55 for each XY position of the wafer W, and is stored in the control unit 300. Remembered.

  Next, the control unit 300 moves (stage swap) the first wafer stage 6A from the measurement station 200 to the exposure station 100 (step S103). Since the wafer W on the first wafer stage 6A is attracted and held by the chuck 7, the relative positional relationship between the reference mark 55 (and the LIPS sensor 54) and the wafer W does not shift during stage swap.

  Next, the controller 300 performs stage alignment at the exposure station 100 (step S104). In this stage alignment, the LIPS mark on the reticle R is irradiated with exposure illumination light, and the image is detected by the LIPS sensor 54 on the first wafer stage 6A. The relative position between the LIPS mark and the LIPS sensor 54 is obtained. Implemented with reference to relationships.

  Next, the control unit 300 causes the exposure station 100 to cause the first focal position measurement unit 5 to measure the position of the surface position of the wafer W in the optical axis direction (first position as focal position measurement information). (Step S105). The X coordinate and Y coordinate of the measurement point MP at this time are set to the same coordinate position in the wafer W as the focus position measurement by the second focus position measurement unit 21 performed in step S102.

  Next, the control unit 300 obtains a difference in the focus direction (and leveling direction) based on the focus position measurement information obtained in step S102 and the focus position measurement information obtained in step S105 (step S106). ). The difference obtained here is a relative shape error between each ZX bar mirror 50, 53 on the exposure station 100 side and each ZX bar mirror 50, 53 on the measurement station 200 side, and a correction amount (correction value) described below. It is. If no shape error has occurred, the difference is zero. On the other hand, the primary component and the shift component of each ZX bar mirror 50, 53 have already been corrected by stage alignment at each station in steps S101 and S104. Accordingly, the fact that a difference is generated here is considered to be a high-order (secondary component or higher) shape error. The difference value may be obtained by substituting with an interpolation point obtained by generating a curved surface from the measurement point MP using a spline function or the like without measuring at the same measurement point MP.

  FIG. 7 shows an example of each measurement result on the exposure station 100 side (measurement in step S105) and the measurement station 200 side (measurement in step S102), and the difference (correction amount) obtained from those results. It is a graph. In FIG. 7, the positions where Y = 0 are extracted in the coordinate system in which the measurement points MP are set at intervals of 2 mm on the X axis and the Y axis, respectively, and the center of the wafer W is (0, 0). That is, the horizontal axis is the X coordinate (nm) of the wafer W, and the vertical axis is the amount of deviation (nm) from the best focus value on the Y axis.

  Next, the control unit 300 determines that a further difference between the difference obtained in step S106 (current difference value) and the difference obtained in the previous correction step (previous difference value) is an allowance for change in shape over time. It is determined whether it is within the range (step S107). Here, when the control unit 300 determines that the value is within the allowable range (YES), the process proceeds to the following step S108. On the other hand, when the control unit 300 determines that it is not within the allowable range (NO), the process proceeds to the error processing step shown in FIG.

  Next, the control unit 300 corrects the higher-order shape error obtained as a difference in step S106 using a correction parameter or a correction table (described later) (step S108). At this time, the focus position measurement information measured on the exposure station 100 side and the measurement station 200 side includes the shape errors of the ZX bar mirrors 50 and 53, respectively. On the other hand, the absolute shape (individual shape itself) of each ZX bar mirror 50, 53 on the exposure station 100 side is previously calibrated based on the exposure result of the test pattern for measuring the focus leveling performance. Has been. Therefore, the correction of the shape error here is performed by matching the shape of each ZX bar mirror 50, 53 on the measurement station 200 side with the shape of each ZX bar mirror 50, 53 on the exposure station 100 side that has already been calibrated. .

  As a specific first correction method of the shape error in step S108, for example, regression analysis is performed from the difference obtained in step S106, and an optimal approximation function parameter (hereinafter referred to as “correction parameter”) is determined. There are ways to use it. The first method is applicable when the deformation shape of each ZX bar mirror 50, 53 over time is known. In such a case, for example, the center part of each ZX bar mirror 50, 53 is lowered in the focus direction due to its own weight deformation or a change in the adhesion portion, and the entire ZX bar mirror 50, 53 is easily deformed so as to have an arcuate shape. Since the gentle deformation represented by the bow can be approximated by a relatively low-order N-order function, it is preferable to determine and use a correction parameter that approximates the difference obtained in step S106 by the N-order function. Become. Further, even when the shape of each ZX bar mirror 50, 53 is deformed so as to be approximated by a higher-order component due to a change in environmental temperature, the approximation function is derived from the difference and the correction parameter is set as described above. It can be determined and used. Further, as a specific second correction method of the shape error in step S108, for example, a bar mirror shape correction table (hereinafter simply referred to as “correction table”) is obtained from the difference for each measurement point MP obtained in step S106. There are ways to create and use. Note that this correction table is prepared for the parameter row for each correction target axis.

  FIG. 8 is a flowchart showing data processing of measurement values obtained by the length measurement mechanism in the present embodiment. First, the control unit 300 obtains a measurement value from each of the interferometers 42, 43, 45, 46, 47, 48, and 51 included in the length measurement mechanism described with reference to FIG. 4 (Step S201). The measurement values obtained here are not obtained in an orthogonal state like the abstract coordinate axes. Therefore, the control unit 300 next executes a process (mode separation process) for converting the measurement value obtained in step S201 into orthogonal components (X, Y, Z, ωx, ωy, ωz components) (step S202). ). Next, the control unit 300 performs a correction process of the shape error caused by the change in the shape (flatness) of the bar mirror (each ZX bar mirror 50, 53) on the measurement value subjected to the mode separation (step S203). Here, the control unit 300 corrects the shape error by using the first and / or second correction methods described above, and specifically, the correction parameter or the correction is performed on the measurement value obtained by mode separation. Add tables. Next, the control unit 300 executes an Abbe correction process on the measurement value subjected to the shape error correction process (step S204). Abbe correction is a function that functionally corrects low-order error components that can occur when the measurement optical axis of each interferometer is tilted or each bar mirror is tilted with respect to the design value. is there. Specifically, the control unit 300 prepares Abbe correction parameters and orthogonality correction parameters in advance, and applies them to the measurement values that have been subjected to shape error correction processing. Here, the measured value subjected to the Abbe correction process becomes the current position in the corrected focus (Z-axis) direction. Thereafter, the control unit 300 reflects the amount of movement required to actually move the wafer stage 6 to the target position based on the Z target value and the corrected current position. The shape error in the leveling (ωy) direction can also be corrected in the same manner as the focus component correction method shown in FIG. 7, and the same control is executed.

  FIG. 9 is a flowchart showing an error processing step that is subsequently executed when it is determined in step S107 of FIG. 6 that the difference is not within the allowable range of change in shape with time (NO). After the error has occurred, first, the control unit 300 has a defect in the lot that has been exposed from the determination in step S107 in the previous correction process to the determination in step S107. The possibility is reported to the online host (step S301). Next, the control unit 300 refers to the shape error table in which the shape error of the ZX bar mirror is recorded, and determines whether the variation amount of the shape error is large or small, that is, whether it can be recovered by feedback correction for the correction table or the like. (Step S302). Here, when the control unit 300 determines that the amount of change is small and can be recovered (small change), the control unit 300 proceeds to the following step S303. Then, the control unit 300 corrects the reflection table, Abbe correction parameter, orthogonality correction parameter, and the like (reflects the fluctuation amount) (step S303), and starts exposure for the subsequent lot. On the other hand, when it is determined in step S302 that the fluctuation amount is large and cannot be recovered (large fluctuation), the control unit 300 displays an error (and an error source bar mirror position, etc.) (step S304). Thereafter, the control unit 300 stops the process by reporting an error status to the online host, and enters a state of waiting for manual assistance.

  In the above description, when the difference between the shapes of the ZX bar mirrors 50 and 53 is measured, that is, when a shape error has occurred, the measurement error is controlled by using a correction table or a correction parameter. It is supposed to be. However, the present invention is not limited to this, and the shape of each ZX bar mirror 50, 53 may be physically changed (directly deformed) by locally changing the temperature. Further, when there are variations in the entire measurement value of the first focal position measurement unit 5 or the second focal position measurement unit 21 and the variation is larger than an allowable value, there is a problem in each focal position measurement unit itself. there is a possibility. Similarly, there may be an inconvenience in adjusting the air-conditioning environment in each station 100, 200. Even in such a case, the control unit 300 may execute a process of generating (displaying) an error notifying that effect and suppressing automatic reflection of the variation amount of the shape error due to an unexpected cause.

  As described above, the exposure apparatus 1 recognizes, during operation of the apparatus, whether or not a relative shape error of a secondary component or higher has occurred in each ZX bar mirror 50, 53 due to, for example, time-lapse, and cannot be ignored. If this occurs, it is reflected in the current position of each wafer stage 6. Conventionally, such a shape error has been corrected after the operation of the exposure apparatus is temporarily stopped after the process wafer or the focus performance inspection wafer is exposed, and the measurement result is verified. On the other hand, the exposure apparatus 1 can perform self-measurement in parallel with periodic maintenance or a process wafer job as a self-verification function. Therefore, since the exposure apparatus 1 can correct the shape error efficiently, that is, while suppressing a decrease in throughput, the movement error that can affect the positioning accuracy of the wafer stage 6 in the focus and leveling direction as a result is efficiently performed. It can be corrected well.

  As described above, according to the present embodiment, it is possible to provide an exposure apparatus and an exposure method that are advantageous in suppressing a decrease in positioning accuracy of a wafer stage that can hold and move a wafer.

  In the above embodiment, a laser interferometer is used as a position measurement system (length measuring mechanism) for measuring the position of each wafer stage 6. However, a two-dimensional encoder is used instead of the laser interferometer. The position of each wafer stage 6 may be measured from the distance. However, in this case, the reference member is, for example, a scale having a plurality of slits, and the index of the correction table for the one-dimensional ZX bar mirror in the above description needs to be expanded two-dimensionally.

  In the above embodiment, the exposure apparatus that projects the pattern of the original plate onto the substrate by the projection optical system is exemplified as the lithography apparatus. However, the lithographic apparatus is not limited thereto, and for example, a pattern may be formed on a substrate with a charged particle beam such as an electron beam, or a pattern is formed by molding an uncured resin (imprint material) with a mold. It may be an imprint apparatus that performs.

(Product Manufacturing Method) A method for manufacturing an article (semiconductor integrated circuit element, liquid crystal display element, recording medium, optical element, etc.) uses the above-described lithography apparatus to form a pattern on a substrate (wafer, glass plate, film substrate). The process to perform is included. Furthermore, the manufacturing method may include a step of performing at least one of development and etching on the substrate on which the pattern has been formed. The manufacturing method may include other processing (processing step) for processing the substrate on which pattern formation has been performed.

  As mentioned above, although embodiment was described, this invention is not limited to said embodiment, A various deformation | transformation and change are possible within the range of the summary.

DESCRIPTION OF SYMBOLS 1 Exposure apparatus 5 1st focus position measurement part 6A 1st wafer stage 6B 2nd wafer stage 21 2nd focus position measurement part 48 1Z Z interferometer 50 ZX bar mirror 51 2Z Z interferometer 53 ZX bar mirror 100 Exposure station 200 Measurement station 300 Control unit W Wafer

Claims (10)

A lithographic apparatus for forming a pattern on a substrate,
A movable substrate holding unit for holding the substrate;
A measurement station that includes a first reference member and that measures a height of the substrate holder and a second meter that measures the height of the surface of the substrate held by the substrate holder; ,
A third measuring instrument that includes a second reference member and that measures the height of the substrate holder is formed on the substrate held by the substrate holder based on the output of the second instrument. A patterning station to be performed;
A control unit,
The pattern forming station includes a fourth measuring instrument that measures the height of the surface of the substrate held by the substrate holding unit,
The controller is configured to detect at least one of the first measuring instrument and the third measuring instrument based on the output of the second measuring instrument and the output of the fourth measuring instrument related to the substrate held by the substrate holding section. Obtain a correction value for the resulting output,
A lithographic apparatus, comprising:   The lithographic apparatus according to claim 1, wherein the control unit obtains the correction value based on a difference between an output of the second measuring instrument and an output of the fourth measuring instrument.   The control unit obtains the correction value based on the output of the second measuring instrument and the output of the fourth measuring instrument regarding the same target location on the surface of the substrate held by the substrate holding unit. A lithographic apparatus according to claim 1 or 2. A plurality of the first measuring instrument and the second measuring instrument, respectively,
4. The control unit according to claim 1, wherein the control unit obtains a correction value relating to an output obtained from at least one of the plurality of first measuring instruments and the plurality of second measuring instruments. 5. The lithographic apparatus according to Item.   The said control part performs the output which concerns on an error based on the output of the said 2nd measuring device regarding the board | substrate hold | maintained at the said board | substrate holding part, and the output of the said 4th measuring instrument. A lithographic apparatus according to any one of claims 4 to 4.   The said 2nd measuring device measures the height of the surface of the board | substrate hold | maintained at the said board | substrate holding part with respect to the reference plane provided in the said board | substrate holding part, The any one of Claim 1 thru | or 5 characterized by the above-mentioned. A lithographic apparatus according to claim 1. The pattern forming station includes a projection system that projects an original pattern onto the substrate,
The said 4th measuring device measures the height of the surface of the board | substrate hold | maintained at the said board | substrate holding part with respect to the reference plane provided in the said board | substrate holding part via the said projection system. A lithographic apparatus according to any one of the preceding claims.   The lithographic apparatus according to claim 1, wherein each of the first reference member and the second reference member includes a mirror or a scale. A plurality of the substrate holders;
The pattern formation for the first substrate at the pattern forming station and the measurement for the second substrate at the measurement station are performed in parallel. The lithographic apparatus described. Forming a pattern on a substrate using the lithographic apparatus according to any one of claims 1 to 9,
A step of processing the substrate on which pattern formation has been performed in the step;
An article manufacturing method comprising:

Images